Tiffany is a farmer. She plants $7$ rows of corn stalks in a field. Each row has $3$ corn stalks. How many corn stalks did Tiffany plant in the field?
Explanation: The number of corn stalks that Tiffany planted is the product of the number of rows that she planted and the number of corn stalks planted in each row. The product is $7\text{ rows of corn stalks} \times 3\text{ corn stalks per row}$ $7\text{ rows of corn stalks} \times 3\text{ corn stalks per row} = 21$ corn stalks